The mechanism of acuity reduction, and the site of involvement, in functional amblyopia are not well understood, however, there is considerable evidence that contrast functions in amblyopic eyes are abnormal. The proposed research is a psychophysical and electrophysiological investigation of contrast sensitivity in amblyopic and nonamblyopic subjects, using sinusoidally modulated light. Contrast thresholds and functions will be determined psychophysically for gratings at various spatial frequencies, and visual evoked responses will be recorded, using the same stimulus conditions. Statistical comparison of psychophysical and electrophysiological data for amblyopic and control subjects will be made, using Fourier analysis. In the second phase of the study electrophysiological data will be collected under binocular conditions, using two haploscopically mounted oscilloscopes, to determine binocular effects, such as suppression. Amblyopic subjects will undergo treatment, and follow-up psychophysical and electrophysiological study will be conducted. This data should: (1) provide insight into the mechanism of amblyopia (2) provide an electrophysiological correlate of amblyopia, and (3) provide a method of evaluating prognosis.